This invention relates generally to electrical interfacing, and, more specifically, to electrical interfacing between a programmable logic controller (PLC) and a converter.
In known electronic systems, interfaces between a PLC and either an ADC or a DAC have typically been implemented with a combination of an application specific integrated circuit (ASIC) and a field programmable gate array (FPGA). Spreading the functionality of the interface across two chips increases the cost and the space requirements. Additionally, scaling of analog data by such interfaces has typically been performed using analog components, which also increases the cost of the interface and the space requirements.
Furthermore, known interfaces have compensated for drift associated with the interface by utilizing calibrating features that occur discretely, either at initial assembly, power up, or at maintenance times. Discrete calibration is typically implemented using either firmware/software or analog hardware, which increases the cost of the interface and requires additional board space. Also, diagnostics features in known interfaces have been implemented using analog components, which also increases the cost and space requirements of the interface. It would be desirable to provide an interface module that implements a data scaling feature, a calibration feature, and a diagnostics feature utilizing a single digital integrated circuit (IC). It would also be desirable for the calibration feature to be continuous over time.
In an exemplary embodiment, an analog interface module includes a high density analog interface (HAI) for electrical interconnection between a programmable logic controller (PLC) and a converter, such as, an analog to digital converter (ADC) or a digital to analog converter (DAC). The HAI includes a data scaling function block for scaling data between two operating modes, a diagnostics function block to verify proper system functionality, a self-calibration function block to compensate for drift associated with the ADC, and a shared register interface function block for electronically connecting the analog input module with a programmable logic controller (PLC).
More particularly, the HAI is a digital application specific integrated circuit (ASIC) that implements an interface from the backplane of a PLC to a family of ADCxe2x80x3s or DACxe2x80x3s. The analog interface module provides data scaling, diagnostics, self-calibration, and a backplane interface using a single ASIC. Combining the different functional features onto a single ASIC reduces cost and saves board space.